Preheat oven to 400F.
Cut cauliflower into small florets and add to large saucepan.
Add 2 cups of water, turn on heat to medium-high, and add a lid.
Let cauliflower cook until fork tender, 10-15 minutes. Dump remaining water.
Add cauliflower to food processor with ghee, salt, and pepper and blend until smooth, scraping down sides as needed. Set aside.
Add avocado oil to a large saucepan. Once hot, add onions, carrots, and mushrooms.
Let veggies saute for 5-7 minutes or until beginning to soften.
Add in garlic, rosemary, thyme, salt, and pepper, and stir until all combined.
Add in ground turkey and cook until no longer pink.
Pour in broth, tomato paste, and Worcestershire sauce. Stir until well combined and let simmer for 5 minutes.
Add in peas and corn, and stir. Turn off heat.
Pour filling into bottom of 9x13 dish.
Add cauliflower mash evenly on top of filling and bake in oven for 20 minutes. Optional: broil for an additional 5 minutes to brown the top.